German state replaces Microsoft Exchange and Outlook with open-source email

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ZDNET’s key takeaways

• Schleswig-Holstein has moved from Microsoft Exchange and Outlook to Open-Xchange and Thunderbird for e-mail.
• Other EU entities have opted for open-source alternatives.
• This switch isn’t just a technical change; it’s a political move.

The German state of Schleswig-Holstein has dumped its government email and calendar systems for open-source software. The six-month migration has replaced Microsoft Exchange and Outlook with Open-Xchange and Mozilla Thunderbird. The transfer covered more than 40,000 mailboxes and over 100 million messages and calendar entries.

Digitalization Minister Dirk Schrödter declared, “Mission accomplished. From the State Chancellery and ministries to the judiciary, police, and other state authorities, our roughly 30,000 employees have embarked on a new path together. We want to become independent of large tech corporations and ensure digital sovereignty. Now we can also say: mission accomplished when it comes to email communication.”

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Schrödter praised the employees who helped make the transition possible: “The past weeks and months have shown that such a transition is no small feat. We are true pioneers. There is hardly a comparable project of this magnitude worldwide. Our sincere thanks go to all employees. Without their support, this transition would not have been possible.”

The switch to open-source email followed years of planning. The state, in concert with open-source vendors such as Nextcloud, has been replacing all proprietary systems with open-source software. Last year, for example, the government began rolling out LibreOffice as the default office suite to replace Microsoft Office.

The minister added that Schleswig-Holstein’s experience will serve as a model for other administrations moving toward open technologies: “We can now use our knowledge, from data analysis to data center monitoring, to support others on the same path.” 

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Many other EU government agencies have already dropped Microsoft software from their computers. These include the Austrian military, Danish government agencies, and the French city of Lyon. The explanation is that many European Union (EU) governmental agencies are sick and tired of relying on American software companies. 

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As the government of Schleswig-Holstein explained in its April 2025 policy statement, Open Innovation and Open Source Strategy: Schleswig-Holstein, looking ahead, “it will be more important than ever to avoid economic or technical dependencies of an individual, monopolistic nature if the state is to maintain control over the IT systems used by it and retain mastery over the data of its citizens and enterprises. For this reason, it is essential to reduce current dependencies and follow the road towards digital sovereignty.”

The state believes open-source software (OSS) is the solution because it “offers an alternative to existing systems on the one hand and is also capable of addressing many of these future changes. That makes OSS one of the most important tools for achieving sovereignty.”

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Digital sovereignty isn’t a phrase often heard in the US, but it’s a big deal in Europe and other countries. It’s not just a case of ‘Proprietary software: Bad and expensive; open-source software: Cheap and good.’ Digital sovereignty has become a major political issue.

European governments, companies, and individuals worry that they can’t trust American-based companies and cloud services to be available when required, or to keep their data safe. As Germany’s digital minister Karsten Wildberger said, Germany and the European Union need to “actively participate in this (sector) as players,” not as customers.

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The rise of digital sovereignty isn’t a new trend. “What we need now in every sector, for every innovation, are European solutions and European sovereignty,” said French President Emmanuel Macron in 2020. He’s made digital sovereignty a central issue in his policies. 

You can expect to see many more European governments, companies, and individuals moving to Linux and open-source software from Windows. This isn’t open-source fan wishful thinking; it’s a fundamental shift in how people see and use office software.

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